5 



CYCLIC MOLECULAR VARIATION 631 



to be converted into normal : that is to say, they now take 

 place by the diminution of resistance. Fig. 387 gives a 

 photographic record of these effects. Selenium cells, again, 

 under normal conditions, respond to light by a diminution 

 of resistance. After tetanisation, or continued application of 

 light, the normal responses, under certain circumstances, 

 undergo an enhancement. The transformation induced by 

 tetanisation, it is interesting to note, also shows itself by the 

 shifting of the base upwards (fig. 388;. 



I have found similar effects, again, to be exhibited by 

 various metallic powders, under the stimulus of electric 

 radiation. The record given in fig. 389 exhibits the 

 abnormal positive response, of increase of resistance, as 

 given by tungsten. After a short period of tetanisation the 

 base-line is seen to be shifted upwards, the molecular 

 condition being transformed, in a negative direction, and 

 thus exhibiting a permanent diminution of resistivity. The 

 response in this particular transformed condition is seen to 



diphasic positive followed by negative. A further 

 period of tetanisation carries this transformation still further 

 in the negative direction, and the individual responses now 

 seen are augmented normal negative. I give also a second 

 pair of records in which the normal response of moderate 

 amplitude in aluminium is enhanced, after an intervening 

 period of tetanisation (fig. 390). 



We have seen, lastly, that molecular response may be 

 recorded by means of the magnetic variation. And it is 

 interesting to see, by employing this mode of record, that 

 under certain conditions tetanisation will enhance magnetic 

 response (fig. 391). 



In order to make a striking demonstration of the fact 

 that the various phenomena described are not the result of 

 some specific property of living tissues, with their hypo- 

 thetical assimilation and dissimilation, but are determined 

 by molecular conditions common to matter both living and 

 inorganic, I shall now give in vertical columns, several series 

 of records of responses, obtained, under parallel conditions, 



